Courses
, Seminars and Mentoring
in Earth Mechanics for geologists and upstream subsurface
engineering are available. Subsurface mechanical problems
are most easily solved through understanding
the earth's governing physics.
Near mudline soil mechanics including compaction are
related to sediment acoustic properties through the
Extended Elastic Equations of Hooke's law.
Deterministic
Earth Mechanical Science for Subsurface
Geoscientists and Engineers
by Phil Holbrook Ph.D.
Drilling safety, efficiency and the production of hydrocarbons
depend on subsurface mechanics. The stresses and fluid
pressures in the earth can be predicted deterministically.
Earth mechanical science is a unification of accepted
physicalmathematical laws that act through the
in situ earth matter. These predictive
laws can be readily understood by subsurface geoscientists
and engineers.
Natural minerals
and fluids
are the minimum energy forms of matter
that compose almost all of the earth. Minerals
and fluids
either rest or move toward lower energy positions under
the direct influence of physical laws. Physical first
principles and conservation laws apply below the earth’s
surface as well as above.
Hydrocarbon move with water until their capillary pressure
is less than the pore throat or fracture entry pressure.
Fracture permeability is highly stress dependant while
intergranular permeability is lithology
and porosity
dependant. Hydrocarbon traps are local fluid
energy minima. They can be detected through
reflection seismic means and mechanically verified before
the risk and expense of drilling.
Blowouts, wellbore collapse, and lower hydrocarbon
production are unwanted consequences of poor mechanical
understanding. Deterministic earth mechanical science
provides physical understanding for good decision making.
Deterministic earth mechanical science has the fewest
possible fitting coefficients. Mass, energy,
and depth linkages are dimensionally correct. All subsurface
stresses
and pressures
depend upon the tectonic regime, porosity, mineral
and fluid
properties. Most of these are known a priori
and can be verified in whole or part through independent
measurements.
There are three discrete energy minima
that correspond with the earths three tectonic regimes.
They occur along 1.) leading, 2.) sheared, or 3.) trailing
plate margins. [Massenergy]
and [stress/strain]
are both conserved in three mechanically compatible
closed forms. Their combined deterministic explanations
are globally applicable for planet earth.
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Who
should take this course?
Anyone with decision making authority in well planning,
drilling, or reservoir production. Well bore diameter
and casing point selection are codependant variables
for every drilling prospect. The elimination of unnecessary
casing strings by judicious choices of casing seat depths
can save millions of dollars in drilling costs. These
decisions depend on lithology,
fluid pressure
and stress. Small changes in casing
seat selections can result in significant changes in
drilling costs. RETURN
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Course
Description and Outline
TPrior
art methods involve only slight variations of (empirical
depth function) forced fitting. Tweaking empirical energydepth
functions is dimensionally and conceptually incorrect.
It is a never ending, subjective, and uncertain process.
Some of the theory of deterministic earth mechanical
science must be taught whatever the practical application.
Well planners, drillers and reservoir engineers have
different needs that could shorten or lengthen some
parts of a comprehensive course. The outline below is
a full course menu from which some might choose to learn
some things and not others. These audience accommodations
can be made either before or during the course.
Two books contain the whole theory. "Deterministic
Earth Mechanical Science" emphasizes underlying
molecular mechanical and energy minimization theory.
The contributors to the composite theory are duly noted.
"Pore pressure through Earth Mechanical Systems"
emphasizes macrophysical relationships that can be
correlated directly to measurements. Many subsurface
trends are shown in both books as well. The physical
theory book draws upon but does not duplicate the macrophysical
book.
The chapter outlines and list of figures of both books
are available. They are Webbroc.pdf
for "Deterministic Earth Mechanical Science"
and cover_itx.doc.
for "Pore pressure through Earth Mechanical
Systems" . These books are a guide for
a comprehensive earth mechanical course. Some audiences
may be interested in only a few subject areas.
Other related courses on borehole wall mechanics, drilling
mechanics, elastic acoustic rock responses, and petrophysical
relationships can also be taught. These are all mechanically
interdependant but are not fully covered in the two
published books.
Short courses from 2 hours to
4 days are available depending on the level of detail
that is wanted. Introductory seminars that cover the
both theory and application in about one hour can also
be presented.
The sample short course described below is a oneday
course that was taught to rock mechanics professionals.
Other courses directed toward Geophysicists, Drilling
Engineers and Pore pressure professionals . Each technical
specialty depends on earth mechanics which can be calculated
and predicted deterministically!
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Pore pressure through Earth
Mechanical Systems
The North American Rock Mechanics Association Short
Course
presented at DCROCKS July 7, 2001 Washington,
DC
Minerals
and fluids are
the earth’s molecular scale building blocks. All
loads, effective stresses and pressures are generated
by and transmitted through minerals
and fluids.
"Pore pressure through Earth Mechanical
Systems", explains earth mechanics
as constitutive pressurestress/strain relationships.
Mineral
ionic bonds can support stress anisotropy. Fluid
compressibility is volumetric and isotropic.
The earth subsurface environment is now understood through
physically representative, closedform mathematical
formulations. These incorporate the governing physical
laws. Earth mechanical systems are force balanced, and
dimensionally correct in closed mathematical forms.
Earth in situ mechanical systems are quantitatively
related to the mineral
and fluid
substances of the earth.
Pore
pressure through Earth Mechanical Systems is recommended
for geologist and engineers that are involved in subsurface
drilling or engineering. Earth mechanical systems relate
rock properties directly to their in situ load environment.
The mechanical interactions between pore fluid pressure
(P_{P}),
fracture propagation pressure (P_{F}), overburden
(S_{v}), average mineralogy, and porosity of
sedimentary rocks are explained through recently formulated
earth mechanical systems. RETURN
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COURSE
OUTLINE 1.) The controlling physics:
Newtonian gravitation is balanced against absolute in
situ strain under Effective Stress Theorem boundary
conditions. Stress/strain hysteresis in granular solids
is related to endmember mechanical systems. Borehole
in situ leakoff tests are directly related to their
far field stress limits. 2.) The primary controls
of grainmatrix compaction are mineral grain hardness
and clay mineral interparticle repulsive force. 3.)
Claystone endmember and nonclay mineral compaction
curves are demonstrated to be powerlaw in situ effective
stress/strain functions.
4.) Minimum horizontal effective stress is directly
related to in situ strain in Normal Fault Regime »
biaxial basins. Stress ratios in strikeslip tectonic
regimes also tend strongly toward even number proportionality.
5.) Mineralogically sensitive porosity transforms for
gg density; resistivity and fullwaveform sonic sensors
are explained.
6.) Overburden, Pore pressure and Fracture propagation
pressure are mathematically defined as loads within
the earth grainmatrixcompactional mechanical system.
This mechanical system of equations uses only material
property coefficients of minerals and fluids that compose
the earth.
Some indirect earth mechanical system interrelationships
are; 7.) Pore pressure within continuous permeable "pressure
compartments" is regulated by the minimum work
fracture pressure. 8.) HPHT fluid expansion pore pressure
is measurable using a regionally calibrated unloading
limb effective stress/strain relationship. The calibration
procedure and its mechanical significance are related
and described.
Empirical "Normal compaction vs. depth trend"
pore pressure methods have existed for 35 years. The
important aspects of these 250+ nonphysical empirical
methods and their operator forced intersections with
earth’s mechanical systems are explained.
Following this course, the student should have a fundamental
understanding of a.) The sensor specific transforms
that are used to estimate porosity and mineralogy; b.)
The grainmatrix loading and unloading limb effective
stress/strain relationships and c.) Earth pore
pressure « effective stress
interactions that regulate pore pressure profiles in
the subsurface. These earth mechanical system interdependencies
relate the loads, effective stresses, pore pressure
to physical properties at the borehole wall. Many drilling
and reservoir engineering applications depend on all
this borehole wall information. RETURN
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COURSE SCHEDULE
Pore pressure through Earth Mechanical Systems
8:30 – 9:00 The controlling physics; Newtonian
gravitation is balanced by absolute in situ strain under
Effective Stress Theorem boundary conditions. Stress/strain
hysteresis in granular solids is related to endmember
mechanical systems. The relationships of borehole leakoff
tests to the limiting farfield stresses is explained
and demonstrated.
9:00  9:30 The primary controls of grainmatrix
compaction are intramineralgrain hardness
and clay mineral interparticle repulsive force.
Both are powerlaw relationships.
9:30  10.00 Claystone endmember and nonclay
mineral compaction vs. depth curves are demonstrated
to be mechanically representative powerlaw linear in
situ effective stress/strain functions.
10:00 – 10:30 Break & Informal Q&A.
10:30 – 11:00 h/v stress ratio; Stress
is transmitted across a given fault block through the
rock grain matrix. Within each Andersonian fault regime
block, there are apparently fixed stress/stress and
stress/strain ratios. Minimum horizontal/vertical effective
stress is directly related to in situ strain in Normal
Fault Regime » biaxial basins. A simple mathematical
H>v>h effective stress ratio/strain relationship
is also apparent in StrikeSlip basins.
11:00 – 12:00 Mineral and fluid sensitive porosity
transforms for gg density, resistivity
and fullwaveform sonic sensors are physical properties
interrelated and explained.
12:00 – 1:30 Lunch with open discussions;
1:30 – 2:00 Closedform grainmatrixcompactional
mechanical systems: Pore pressure and Fracture propagation
pressure are mathematically defined as interdependant
loads within the earth grainmatrixcompactional mechanical
system. The relationship between the elastic, and grainmatrixcompactional,
mechanical system domains are explained.
2:00 – 2:30 Indirect earth mechanical system
interrelationships: Pore pressure within continuous
permeable "pressure compartments" is regulated
by the minimum work fracture pressure of that compartment.
The nature of this mechanical system is explained.
2:30 – 3:00 HPHT fluid expansion pore pressure
is measured using a regionally calibrated unloading
limb effective stress/strain relationship. The calibration
procedure and its mechanical loading vs. unloading
significance are related, explained and described.
3:00 – 3:30 Break & Informal Q&A.
3:30 – 4:00 Earth Mechanical Systems vs. Porosity
Relationships: All the elastic (Hooke’s law),
grainmatrixcompactional, and unloading effective
stress/strain functions are mathematically and compositionally
related powerlaw linear earth’s mechanical systems.
4:00 – 4:30 Empirical "Normal compaction
vs. depth trend" pore pressure methods have
existed for 35 years. There are 250+ nonphysical methods.
Empirical pore pressure methods are tangential approximations
to earth mechanical systems. Apparent success occurs
when the operator forces nonphysical intersections
with the earth’s mechanical systems. Empirical
curve fit methods do not use mechanical boundary condition.
Strain is not used. Stresses and strain are not balanced
and units do not cancel.
4:30 – 5:00 Earth Mechanical Systems Summary;
The earth has several mechanical systems that relate
stress/strain to mineralogy and porosity. Hooke’s
law and the grainmatrixcompactional mechanical system
are analogous and related to each other. The Effective
Stress Theorem boundary condition is fundamentally related
to volumetric in situ strain in closed mathematical
form.
5:00 Adjourn
Following this course, each student should have a fundamental
understanding of a.) The sensor specific transforms
that are used to estimate porosity and mineralogy; b.)
The grainmatrix loading and unloading limb effective
stress/strain relationships and c.) Earth pore pressure
« effective stress interactions that regulate
pore pressure profiles in the subsurface. These earth
mechanical system interdependencies directly relate
the loads, effective stresses, pore pressure and physical
properties at the borehole wall. Many drilling and reservoir
engineering applications depend on this information.
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BIOGRAPHY
OF LECTURER
Phil Holbrook received his Ph.D. in Geology from Penn
State in 1973. He entered Gulf Oil Company’s one
year Experience Broadening program in Exploration Geophysics.
In exploration operations, he interpreted seismic data,
developed drilling prospects, and supervised acquisition
of geophysical data and well logging. He subsequently
coordinated Gulf’s EB program and performed research
on petrophysical oil exploration applications. He worked
at Exxon Production Research for 8 years doing reservoir
studies, seismic well ties, borehole televiewer operations,
and served as an internal well log analyst  petrophysicist
consultant to Exxon’s operations divisions.
He joined SperrySun and began work on the only mechanically
representative pore pressure and fracture pressure prediction
methodology in 1985. This physically representative
methodology has been applied to over 300 wells worldwide.
He has studied earth mechanics, written two books and
over 25 technical papers. Presently he consults on petrophysics,
earth in situ and borehole relative force balance and
rock mechanics. He performs applications research projects;
and teaches on these subjects that are important to
earth science. The earth mechanical system limits most
oilfield mechanical operations such as drilling, setting
casing, completion and reservoir mechanics.
For Courses, Seminars and/or Mentoring
information you can contact Phil Holbrook by email
phil@forcebalanced.net
for details. RETURN
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